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  • 1
    Electronic Resource
    Electronic Resource
    Structural and dynamical properties of Cu–Au bimetallic clusters (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 1056-1066 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effect of alloying on the structural and thermal properties of Cun−xAux (n=13,14) clusters is investigated by constant energy Molecular Dynamics simulations. The interactions between the atoms in the clusters are mimicked by a many-body (Gupta-like) potential based on the second moment approximation to the tight-binding model. The minimum energy structures and the lowest-lying isomers of the pure and mixed clusters are obtained by thermal quenching. We find icosahedral-like ground state structures for the 13- and 14-atom clusters and for all the concentrations, the only exception being Au14 which has C6v symmetry. Mixed structures are preferred over the segregated ones. The lowest-lying isomers of the binary clusters are the permutational ones, i.e., isomers having the same underlying geometry as the ground state structure and different relative arrangement of the unlike atoms in the atomic positions of the geometry. However, presence of these low lying permutational isomers does not affect the gross features of the melting-like transition. The 13- and 14-atom (icosahedral-like) binary clusters melt in one and two stages, respectively, as the corresponding pure Cu clusters. In constrast the melting-like transition of Au14 exhibits a single stage. The melting temperature is studied as a function of cluster concentration and size. The main conclusion is that mixed Cu–Au clusters likely behave as pure Cu clusters, both from the structural and the dynamical points of view, for all concentrations. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470831
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  • 2
    Electronic Resource
    Electronic Resource
    On the problem of fitting many-body potentials. I. The minimal maximum error scheme and the paradigm of metal systems (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 8899-8911 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Issues involved in fitting a semiempirical potential, such as the choice of a goodness criterion, selection of fitting quantities (properties), ascription of the degree of importance to the individual members of a fitting set, etc., all of which affect the outcome of a fitting procedure, are addressed and analyzed. The minimal maximum error fitting scheme is implemented to obtain the values of the parameters of the Gupta-type potential for nickel. The subtleties of this potential, one of which is that only four of its five parameters are independent, and their implications are pointed out and discussed. The resulting values of the parameters for nickel are analyzed and compared with those obtained in earlier studies. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478809
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  • 3
    Electronic Resource
    Electronic Resource
    Use of agricultural wastes for xanthan production by Xanthomonas campestris (1998)
    Springer
    Journal of industrial microbiology and biotechnology 21 (1998), S. 242-246 
    Details
    ISSN: 1476-5535
    Keywords: Keywords: xanthan; agricultural wastes; Xanthomonas campestris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Four different acid-hydrolyzed wastes, from melon, watermelon, cucumber and tomato were compared for xanthan production. Growth of Xanthomonas campestris, xanthan biosynthesis, kinetics and chemical composition were investigated. Both growth and xanthan production were dependent on the acid hydrolysate concentrations and available nitrogen. Melon acid hydrolyzed waste was the best substrate for xanthan production. Exopolysaccharide obtained throughout this study was compared to commercial xanthan, showing a very similar chemical composition. Acid hydrolyzed wastes are proposed as a new carbon source for xanthan production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/sj.jim.2900582
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  • 4
    Electronic Resource
    Electronic Resource
    Annual cycle of expression of connective tissue polypeptide markers in the mantle of the musselMytilus galloprovincialis (1996)
    Springer
    Marine biology 126 (1996), S. 77-89 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We suggest that gonad development in the mantle tissue of the bivalve molluscMytilus galloprovincialis Lmk. is an example of epithelial/mesenchymal interactions (i.e. soma/germline interactions) and morphogenesis in the adult state. According to this concept, the aim of the present study was to use biochemical and immunochemical methods for identifying and characterizing the mantle cell polypeptide markers whose expression is seasonally and morphogenetically regulated. We showed for the first time thatM. galloprovincialis mantle, of both males and females, contains polypeptides (with an apparent mol. wt of 45 to 53 kDa) specific for connective tissue (“mantle connective tissue polypeptides”; MCTPs). Electrophoretic, immunoblotting and immunofluorescent experiments demonstrated that MCTPs are primarily localized in the adipogranular (ADG) cells, and their expression in the mantle is seasonally regulated. There is a positive correlation between MCTP expression and connective tissue volume in the mantle. MCTPs are overexpressed during the rest period, when the mantle consists of connective tissue mainly, whereas mature gonads contain only trace amounts of MCTPs. Moreover, there is a temporal correlation between the onset and decrease of MCTP expression and the appearance and disappearance of the ADG cells in the mantle. MCTP localization in the mantle tissue should not be associated with the ADG cells only, because positive immunofluorescence was also detected in follicle membranes (but not in germ cells) and superficial mantle epithelium. Using immunoblotting and immunofluorescence, MCTPs were found in the connective tissue of the mantle, posterior adductor muscle and visceral mass, but not gills, foot or hepatopancreas. Possible mechanisms by which MCTPs could participate in the annual processes of mantle gonad/connective tissue development and involution are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571379
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  • 5
    Electronic Resource
    Electronic Resource
    Electronic and atomic structure of Na, Mg, Al and Pb clusters (1988)
    Springer
    The European physical journal 11 (1988), S. 163-174 
    Details
    ISSN: 1434-6079
    Keywords: 36.40 ; 31.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Density functional theory is used to study the electronic and atomic structure of small clusters of Na, Mg, Al and Pb. We study the quantityE N−1–E N , which has relevance to the processes of cluster growth and evaporation (E N is the total energy of the cluster withN atoms). By comparing the results of the jellium model with those of a more realistic model (although still simple) we are able to appreciate “structural” effects beyond the “electronic-shell effects” which form the essence of the predictions of the jellium model. The calculations predict formation of atomic shells and appreciable reconstruction as the cluster grows.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01444433
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  • 6
    Electronic Resource
    Electronic Resource
    Enrichment and segregation in alkali heteroclusters (1989)
    Springer
    The European physical journal 12 (1989), S. 237-239 
    Details
    ISSN: 1434-6079
    Keywords: 31.20 ; 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A spherical average pseudopotential method (SAPS) is used to investigate some properties of compound alkali clusters. The effect that the substitution of a Sodium atom by a Lithium atom in a Na n cluster has on the stabilities and geometries is studied forn≤21. We have found that substitution is always energetically possible. On the other hand equiatomic Na n Cs n clusters are considered in the size rangen≤16. We find a strong segregation effect of the Cesium atoms towards the cluster surface. This agrees with what happens in liquid Na x Cs1−x alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426946
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  • 7
    Electronic Resource
    Electronic Resource
    Stability of isomeric Na n clusters (1991)
    Springer
    The European physical journal 19 (1991), S. 141-143 
    Details
    ISSN: 1434-6079
    Keywords: 31.20.Sy ; 36.40. +d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A method which combines density functional theory and the use of pseudopotentials is applied to obtain ground state and low-lying metastable geometries of Na n clusters (7≤n≤40). The large variation in the magnitude of energy gaps between isomers suggests that the melting temperature is not a simple monotonous function of size. A detailed study of the differences between electronically stabilized (n=8, 20, 40) and structurally stabilized (n=13) clusters suggests some clues to understand the intriguing behaviour of Na13.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01448275
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  • 8
    Electronic Resource
    Electronic Resource
    Evaporation rates of hot sodium clusters (1991)
    Springer
    The European physical journal 20 (1991), S. 119-122 
    Details
    ISSN: 1434-6079
    Keywords: 36.40. + d ; 31.20.Sy ; 65.50. + m ; 63.70. + h
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A scheme based in density functional theory with pseudopotentials is used to obtain the normal modes of vibration of Na n clusters (4 ≤n ≤ 22). The monomer and dimer evaporation rates from thermally excited clusters are obtained in this harmonic approximation. The time evolution of the abundance spectra from an initial uniform mass distribution of hot clusters is studied and its influence in the experimentally observed spectra is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01543952
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  • 9
    Electronic Resource
    Electronic Resource
    Vibrational frequencies of sodium clustersWork presented at “Thirty Years of Density Functional Theory: Concepts and Applications,” Cracow, Poland, June 13-16, 1994. (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 56 (1995), S. 589-601 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The vibrational frequencies of NaN clusters (2 ≤ N ≤ 72) are calculated by direct diagonalization of the dynamical matrix. Density functional theory with a spherically averaged pseudopotential is used to compute the total energy. The geometry is optimized by the simulated annealing technique. Contributions to the Hessian matrix due to electron relaxation following the ionic displacements are calculated in linear response theory. The frequencies are in the range 0-220 cm-1 and the electron relaxation strongly modifies those of the modes dominated by radial oscillations, particularly the breathing mode frequencies that are proportional to N-1/3. The filling of atomic shells produces a stepwise behavior of the highest frequencies. The giant dipole resonance energies are obtained as a byproduct of the calculation. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560560515
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  • 10
    Electronic Resource
    Electronic Resource
    Ionic vibrational breathing mode of metallic clusters (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 61 (1997), S. 613-626 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The energy of the vibrational mode with spherical symmetry, in which the ionic cores oscillate in the radial direction around the equilibrium geometry (ionic breathing mode) is calculated for trivalent (AlN, 2≤N≤50) and monovalent (NaN, 2≤N≤73; CsN, 2≤N≤74) metallic clusters. The ground-state total energy is calculated using density functional theory, with a spherically averaged pseudopotential to describe the ion-electron interaction and optimizing the geometry by the simulated annealing technique. The energy of the ionic mode is calculated by diagonalization of the dynamical matrix including the electronic relaxation in the linear response approximation. The compressibility and bulk modulus of the metallic cluster are obtained from the energies of the monopole oscillations. These energies present a linear behavior on the inverse of the cluster radius, which is analyzed using a semiclassical liquid drop mass formula for the total energy of the clusters and a scaling model. The values of the vibrational frequencies present electronic shell closing effects for the three metals.©1997 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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